Means for controlling energy delivered to electrical translating devices.



No. 656,821. Patented Aug. 23, I900. H. W. LEDNARD.

MEANS FOR CONTROLLING ENERGY DELIVERED T0 ELECTRICAL TRANSLATING DEVICES.

(Application filed Jan. 13, 1900.)

(No Model.)

UNITED STATES PATENT OFFICE.

HARRY WARD LEONARD, OF NEW YORK, N. Y.

MEANS FOR CONTROLLING ENERGY DELIVERED T0 ELECTRICAL TRANSLATING DEVICES.

SPECIFICATION forming part of Letters Patent No. 656,821, dated August-.28, 1900.

Original application filed January 31, 1896, Serial No, 577,520. Divided and this application filed January 13, 1900. Serial No. 1,296. (No modeh) To all whom it may concern:

Be it known that I, HARRY WARD LEONARD, a citizen of the United States, residing in the borough of Manhattan, city of New York, State of New York, have invented a certain new and useful improvement in Means for Controlling the Energy Delivered to Electrical Translating Devices, of which the following is a description.

My invention relates to systems of electrical distribution, and more especially to systems in which a practically-constant electromotive force exists between the supply-conductors and from which conductors energy must be taken for operating devices requiring at times a different electromotive force from that upon the supply-conductors.

The principal object of my invention is to furnish an improved method and means for producing at will upon the terminals of the translating devices any electromotive force with the least possible waste of energy. This makes it necessary that the number of watts taken from the source of energy be practically the same as that absorbed by the translating device or devices in use.

For incandescent lamps and similar devices which cannot commercially be made higher than a certain voltage the cost of supply-conductors for operating them at a distance becomes uncommercially high unless the electric energy is transmitted at a voltage higher than that of the lamps. A constant electromotive-force multiple-arc system is best both for the transmission and for the circuits to which the translating devices are connected. \Vith the alternating systems this conversion of the energy from a higher to a lower voltage is readily accomplished by means of the wellknowncon verters; but electric energy in this form is not adapted to the operation of the best forms of motors, which require a continuous current, nor for storage batteries, electrolytic Work, and many other uses.

I11 the accompanying drawings, Figures 1, 2, 3, and 4 illustrate old methods of supplying translating devices with an electromotive force different from that upon the main supply-conductors, and Figs. 5 and 6 illustrate my improved method of accomplishing this result.

The Edison three-Wire system is one familiar example of the method of securing the advantages of a higher electromotive force than that of the translating devices for the transmission and securing without waste lower electromotive forces controllable at will and practically constant independent of the current. This system is illustrated in Fig. l of the drawings, in which S and S are two generators connected in series and from which extend the main positive and negative wires P and N, and from between the two machines extends the neutral or compensating conductor'G. If the electromotive force of each of the generators S and S is one hundred volts, the total electromotive force across the outside conductors P and N will be two hundred volts and the translating devices a, connected between the outside conductors and the neutral conductorthat is, two in serieswill each receive an electromotive force of one hundred volts, as is well understood.

In a modification of the Edison three-wire system, which is illustrated in Fig. 2 of the drawings, a rheostat R is placed across the outside conductors P and N, which rheostat is constantly in circuit. It will be evident that the potential along the conductor in this rheostat would depend upon the current flowing and the ohms the current had passed through. In this arrangement only one main generator S is necessarily employed, and this generator, we will assume, produces an electromotive force of two hundred volts. Hence there would be a difference of potential across the outside conductors of two hundred volts. The handle of the rheostat is connected to the neutral or compensating conductor 0, and if we place translating devices a between the outside conductors and the compensatingconductor an electromotive force of one hundred volts could be maintained at the terminals of the translating devices, as by moving the handle of the rheostat to vary the resistance in circuitoneither side of the compensating-conductor there could be maintained upon the conductor 0 any potential desired intermediate between that of P and N. In practice with one-hundred-volt incandescent lamps the potential upon the conductor 0 would be so maintained that the electromotive force between the conductors P and O and O of these machines are shunted by a rheostat R and N would be one hundred volts; but this method involves a decided loss of energy, and

another decided objection is that since the potential of the conductor 0 depends upon the drop of potential in the conductor of the rheostat, which in turn depends upon the relative number of amperes on the two sides of the system, it will be evident that more than one-half of the total energy would be wasted in case all the translating devices were connected between the conductor 0 and one of the outside conductors.

Another method of securing the benefit of high constant electromotive force available at the translating devices at a lower constant electromotive force, as heretofore proposed, is illustrated in Fig. 8, in which S is the source of constant electromotive force, and B is a storage battery connected across the outside conductors P and N, and O is the compensating-conductor. By connecting the conductor O at various points along the storage battery any desired constant electromotive force from zero to the full electromotive force between P and N can be obtained at the terminals of the translating devices. By moving the connection of the conductor 0 along the battery B the electromotive force upon the translating devices, while constant so far as being affected by the current is concerned, could be made variable at will without the waste of power incidental to the use of the idle resistance (illustratedin Fig. 2) and without the variation in electromotive force due to the amount of current flowing. A similar arrangement is illustrated in Fig. 1, the fieldmagnet of the motor a being connected across the outside conductors, so as to have a constant field of full strength, and the armature is connected between the conductor G, ex tending from the storage batteries B, and the outside conductor I. This method is illustrated in Figs. 4; and 5 of my Patent No. $783M, dated July 5, 1892, and a somewhat similar arrangement is illustrated in my Patent No. 476,5H, dated June '7, 1802.

My present invention consists principally in substituting dynamo-electric rotary transformers for the storage batteries in Figs. 4 and 5 of my Patent No. 178,344, above referred to.

In Fig. 5 of the accompanying drawings my invention is illustrated in its simplest form. In that figure S represents the source of constant electromotive force, provided with a rheostat for controlling the electromotive force produced. From this source extends the main conductors P and N. Across the circuit P N, I place two dynamo-electric inachines 1 and 2 of the ordinary type-that is, such as would be adapted to be operated by being connected in shunt across the circuit P N. These two machines have their armatures mechanically connected together and electrically in series across the circuit P N, and their field-magnets are also connected in series across this circuit. The field-magnets proximately that of the source S.

of high resistance, the contact-lever of which is connected between the field-circuit of the two machines. It the contact-lever of this rheostat is at its central position, the fieldmagnets of both machines will be equally excited, and since each field is wound to be excited by the full electromotive force of the source S the current through each of the fieldmagnets under such conditions will be onehalf the full exciting-current. tures of these machines being in series with each other will receive a current and will run at such a speed that their combined counter electromotive force will be practically equal to that of the source S-that is, both machines will each produce a counter electromotive t'orce one-half of that of S, and to do this with a field of about one-half strength they must run at about their full speed. The translating device 3, which is illustrated as a motor and upon the terminals of which it is desired to obtain a variable electromotive force, is connected in a circuit 0, extending from the armature-circuit of machines 1 and 2 intermediate the two machines to the outside conductor N, the field-magnet of the motor being connected across the circuit P N. The conductor 0 has a potential which is intermediate between that of P and N, as in the arrangement illustrated in Figs. 1, 2, and 3. The potential upon the conductor 0 can be varied at will by varying the electrometive force produced by the armatures of the machines 1 and 2, and this variation is accomplished by varying the field strength of those machines by means of the rheost-at R. Since the armatures of the machines are mechanically connected together, their speeds must be equal, and since they are electrically connected in series their total electromotive force will always be approximately equal to that of the main source S; but the electrometive force of either may be varied from zero to approximately the full electromotive force of S. This is accomplished byadjusting the contact-arm of the rheostat R from one extreme position to the other,whereb the field of either machine may be short-circuited and the other will receive the full electromotive force of the line. hen the electromotive force of either of the machines 1 and 2 is zero, the electrometive force of the other will be approximately that of the line, so that it is evident that by adjusting the contact-lever of the rheostat any desired potential can be obtained upon the conductor 0 from the potential of Pto that of N, and hence any desired electromotive force between the conductors G and N from zero to that between P and N, and in the case of an electric motor whose armature is connected between the conductors O and N,with its field constant across the main-line conductors P and N,it is evidentthat there may be delivered upon the terminals of the armature of that machine any eleotromotive force from zero to ap- Hence the The arma- IIO motor 3 can be run from rest to full speed without the use of rheostats or other wasteful controlling devices. As an illustration, let it be assumed that the electromotive force of the source S is five hundred volts, that the machines 1, 2, and 3 are each wound to stand an electromotive force of five hundred volts and one hundred amperes, that the contactarm of the rheostat R is in the position at which the field-magnet of the machine 2 is short-circuited, and that consequently there is no electromotive force between the conductors O and N, and the motor 3 will be at rest. It now it is desired to start the motor 3 and run it at its highest speed, and assuming that for starting the motor there is required one hundred amperes through the armature and fifty volts at its terminals, the distribution of electromotive forces and currents will be as follows, neglecting, for the sake of simplicity, the slight mechanical and electrical losses in the field-magnets and armatures and at the bearings due to conversion of enegy into heat: From theline P there will flow ten amperes, the armature of the machine 1 having an electromotive force of four hundred and fifty volts, and the armature of the machine 2 will have an electromotive force of fifty volts--that is, the same electromotive force as the armature of the motor 3. The field-magnet of the machine 1 not being at fulLstrength, the armature of that machine will tend to run faster, but cannot, owing to the fact that it is opposed by the production of current in the machine 2, which current is supplied to the motor 3. The four thousand five hundred watts (four hundred and fifty volts multiplied by ten am peres) absorbed by the machine 1 are transformed into mechanical power in the shape of speed and torque in the shaft joining the armatures of 1 and 2 and reappear as electrical energy in the armature of 2 in the form of fifty volts and ninety amperes, equaling four thousand five hundred watts. The ten amperes from the line after passing through the armature of the machine 1 join with the ninety amperes produced by the machine 2 as a generator, and the total of one hundred amperes at fifty volts is supplied to the armature of the motor 3. Thus it will be seen that by the use of ten amperes from the five hundred-volt line we operate at one-tenth speed a motor requiring one hundred am peres. By the methods of series-parallel control heretofore employed at least fifty amperes from the line would be required instead of ten. If now the contact-arm of the rheostat is gradually moved to the other extreme position, so that the field-magnetof the machine 2 is fully excited and that of the machine 1 is short-circnited, the electromotive force upon the terminals of the motor 3 will be gradually increased up to the full-line pressure of five hundred volts. If the torque of the motor 3 be practically constant, as in the case of an electric locomotive slowly accelerated upon a constant grade, the amperes required would be the same for the slow speed and full speed. At full speed there would be one hundred amperes passing through the machines 1 and 3 in series and practically no current through the machine 2. If now it is desired to bring the locomotive to rest, the contact arm of the rheostat is gradually moved to an opposite position to weaken the field of the machine 2. The momentum will cause the motor 3 to continue for an instant at full speed, and since that machine has a constant field its electromotive force will continue constant for the same period and the electromotive force of the machine 2 falls rapidly, due to its weakened field, and hence the motor 3 becomes a generator supplying current to the armature of the machine 2 in a field which is growing weaker. The weakening of the field of the machine 2 tends to cause the armature of that machine to increase in speed, but in doing so itis met, with opposition due to the revolution of the armature of the machine 1'in a field of increasing strength, which causes a development of volts by the machine 1, which are added to the volts produced by the machine 3, and hence exceed the line-volts and cause a current to flow back onto the line. This condition continues in a decreasing degree until the machine 3 produces no volts, and therefore the machine 2 will have no Volts upon its terminals, and hence the machine 1 will have five hundred volts upon its terminals, which means that the machine 3 will be at rest. Thus the energy represented by a moving body driven by an electric motor by my improved method can be utilized and fed back onto the line as useful electric energy 'in stead of being wasted, as heretofore. The amount of energy fed onto the line in this way is greater when the contact-lever of the rheostat is first thrown over and while the speed of momentum of the locomotive is greatest, and as the speed and momentum decrease the amount of current fed back onto the line decreases. This makes a very rapid but extremely-smooth stop. The acceleration of a body from rest to full speed is similarly quite rapid and very smooth.

From the foregoing it will be seen that the function and performance of the rotary transformers 1 and 2 are quite similar to that of the storage batteries shown in my Patent No. 478,344, except that in the present case one terminal of the motor must necessarily be connected to a conductor whose potential remains practically fixed, whereas in my said patent the potential upon each brush is variable over the entire range of potential, perinitting the reversal of the motor and its operation to full speed in the opposite direction, which cannot be done in my present arrangement of apparatus, as illustrated in Fig. 5.

To enable the reversal of the working motor 3 by my present invention, I employ tWo sets of rotary transformers, as shown in Fig.

6, the additional set being represented by the machines 1 and 2 and the regulating-rheostat R. In this arrangement the terminals of the working motor 3 are connected to the conductors C and 0, extending from the armature-circuits intermediate the two machines of each set. By manipulating the contact-arms of the two rheostats any potential from that of P to that of N can be obtained upon the conductors 0 and C. Therefore it is evident that upon the terminals of the working motor 3 any electromotive force from zero up to the full electromotive force of the source S can be had and in either direction.

I do not claim herein the method of controlling electric motors or other translating devices herein described, since that part of my invention is covered in my application, Serial No. 577,520, filed January 31, 18%, of which the present case is a division.

Having now described my invention, what I claim as new, and desire to secure by Letters Patent, is as follows:

1. In a system of electrical distribution, the combination with a main source of supply and a circuit extending therefrom, of two dynamo-electric machines, the arm atures and fieldmagnets of which are independently connected in series across the circuit, an intermediate conductor extending from the armature-circuit of said machines from a point intermediate the two armatures, a translating device connected in a circuit extending from said intermediate conductor to one of the conductors extendingtrom the source of supply, and a rheostat shunted around the field-magnets of the two dynamo-electric machines, by the adjustment of which the strength of each of said field-magnets is varied to vary the potential upon the intermediate conductor, substantially as set forth.

2. In a system otelectrical distribution, the combination with a main source of supplyand a circuit extending therefrom, of two dynamo-electric machines, the armatures of which are mechanically connected together and electrically connected in series across the circuit, and an independent connection across the circuit containing the field-magnets of said machines in series, an intermediate conductor extending from the armature-circuit of said machines from a point intermediate between the two armatures, a translating device connected in a circuit extending from said intermediate conductor to one of the conductors extending from the source of supply, and a rheostat shunted around the field-mag nets of the two dynamo-electric machines, by

the adjustment of which the strength of each of said field-magnets is varied to vary the potential upon the intermediate conductor, sub stantially as set forth.

3. The combination of a main source of supply,a circuit extending therefrom, two sources of electromotive .torce connected therewith, an intermediate conductor extending from each of said last-named sources, and a translating device connected between said latter conductors, substantially as set forth.

4. The combination ofa main source of supply,a circuit extending therefrom, two sources of electromotive force connected therewith, an intermediate conductor extending from each of said last-named sources, a translating device connected between said latter conductors, and means for va 'ying the electromotive force on said last-named conductors, substantia'lly as set forth.

5. The combination of a main source oi supply,a circuitcxtcnding theretrom,two sources of elcctromotive force connected therewith, an intermediate conductor extending from each of said sources, a translating device connected between said conductors, and means for adjusting said two sources of electrometive ljorce to vary the potential upon each of said conductors from that of the positive potential of the supply-circuit to that of the negative potential of the supply-circuit, substantially as set forth.

(3. The combination of a main source of supply, a circuit extending theretrom,two sources of electromotivc force connected across said circuit, each source consisting of two dynamoelectric machines, the armatures and fieldmagnets of which are independently connected in series across the circuit, an intermediate conductor extending from the armatnrc-cir cuit of each of said sources of electromotive [force from a point intermediate the two armatures, a translating device connected between said conductors, and a rheostat shunted around the field-magnets of each pair of dynamo-electric machines comprising the two sources of electromotive force, by the adjustment of which the strength of each of said field magnets is varied to vary the potential upon the intermediate conductors, substantially as set forth.

This specification signed and witnessed this 26th day of December, 1899.

II. WARD LEONARD.

,Vitnesses:

O. E. CARPENTER, W. H. MoOi-rnsnny. 

